Thermodynamic reciprocating machine of the displacer-piston type



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V 7///%/// ///A//%/// 7/ j J. W. L. KUHLER THERMODYNAMIC RECIPROCATING MACHINE OF DISPLACER-PISTON TYPE Nov. 30, 1965 Filed Nov. 14, 1962 \F L- A/A/A/ 2 7 n y W n m .l)... ///%/A/// F IG.1

INVENTOR JACOB W.L.KbHLER 02 5 AGEN w. KOHLER 3,220,177

J. THERMODYNAMIC RECIPROCATING MACHINE OF THE DISPLACER-PISTON TYPE Flled Nov. 14, 1962 4 Sheets-Sheet 2 Nov. 30, 1965 FIG.3

INVENTOR JACOB W. L. KOHLER gild- AGE N Ti Nov. 30, 1965 J. w. L. KOHLER 3,220,177

THERMODYNAMIC RECIPROCATING MACHINE OF THE DISPLACER-PISTON TYPE Filed Nov. 14, 1962 4 Sheets-Sheet 5 FIG.4

XNVENTOR JACOB W.L. KiiHLER BY I Q 5; .2 E.

AGENT Nov. 30, 1965 J. w. L. KOHLER 3,220,177

THERMODYNAMIC RECIPROGATING MACHINE OF THE DISPLACER-PISTON TYPE Filed Nov. 14, 1962 4 Sheets-Sheet 4 FIG.5

I INVENTOR JACOB W.L. K'oHLER United States Patent ware Filed Nov. 14, 1962, Ser. No. 237,497 Claims priority, application Netherlands, Nov. 16, 1961,

2 Claims. ci. 60-24) The invention relates to a thermodynamic reciprocating machine of the displacer-piston type, comprising two identical, parallel crank shafts, which are coupled with each other and are adapted to rotate in synchronism in opposite directions with the same angular speed, these crank shafts being located symmetrically to a plane parallel to the centre lines of the crank shafts and going through the centre line of the machine, said crank shafts co-operating via cranks and crank journals with at least one pair of connecting rod mechanisms, in which the ends of the connections of one mechanism remote from the crank shafts are intercoupled and are located on one side of the plane going through the centre lines of the crank shafts, whereas the corresponding ends of the connecting rods of the other mechanism are also intercoupled and are located on the other side of the plane going through the centre lines of the crank shafts, each of the two connecting rod mechanisms being connected,

in addition, with one or more piston-like bodies.

With a known machine of the kind set forth, which is to denote herein hot-gas reciprocating engines, cold-gas refrigerators and a heat pump, the latter two operating on the so-called reverse hot-gas reciprocating engine principle, the displacer piston and the piston are coupled with the crank shafts so that the latter can perform only identical strokes when the machine is operating. In those cases in which the temperatures in the space above the piston and in the space above the displacer piston exhibit great difference, it may be desirable for the piston and the displacer piston to perform unequal strokes.

To this end the thermodynamic reciprocating machine according to the invention has the feature that the crank journals of each of the crank shafts establishing the connection between said crank shafts and the connecting rods of one mechanism and the crank journals establish ing the connection between said crank shafts and the connecting rods of the other mechanism are spaced apart from the centre line of the crank shaft concerned by such different distances and that the connecting rods have such lengths that the piston-like bodies connected with one connecting-rod mechanism and with the other connecting-rod mechanism perform unequal strokes.

In general the piston-like body connected by the connecting-rod mechanism concerned with the crank journals farthest remote from the centre lines of the crank shafts will perform the larger stroke. With a view to the properties characteristic of the driving gear referred to above the connecting rods connected with the same piston-like body must have the same length. The connecting rods of one pair of one mechanism and the connecting rods of the other pair of the same mechanism may have different lengths. The crank journals, spaced apart, as stated above, by different distances from the centre line of the crank shaft concerned, may be located in planes going through the centre line of said crank shaft and being at an angle to each other. A further great advantage of this driving gear resides in that unequal strokes of the piston and of the displacer can be obtained, while nevertheless a satisfactory and simple seal between the crank case and the cylinder can be "ice obtained, so that the pressure in the crank case may be equal to the ambient pressure.

In its most general form described above, the driving gear according to the invention can, in general, not be balanced completely. Particularly in the case of multicylinder machines an accurate balancing of the driving gear may sometimes be of minor importance. With onecylinder machines and also with multi-cylinder machines employed in places where vibrations are highly undesirable the balancing problem plays a very important part.

In order to obtain complete balancing of the thermodynamic reciprocating machine it is characterized, in a further advantageous embodiment, in that the crank journals of each of the crank shafts, establishing the connection between these crank shafts and the two connecting rod mechanisms, are located substantially in one plane going through the centre line of the crank shaft concerned, while the dimensions of the machine fulfill otherwise substantially the following equation:

wherein r, and r designate the distances of the crank journals connecting the connecting rods of the first and of the second mechanism respectively with the crank shafts from the centre line of the chank shaft concerned respectively, l and I denote the lengths of the connecting rods of the first and of the second mechanism respectively, c and e are the distances of the projections of the ends of the connecting rods of the first and of the second mechanism respectively remote from the crank shafts on the plane going through the centre lines of the crank shafts from the centre line of the crank shaft concerned, m and m are the masses of the parts reciprocating in the direction of the centre line of the mach-inc, which parts are connected with the connecting rods of the first and of the second mechanism concerned, each mass having added to it that part of the connecting rod mass which is to be added, for balancing purposes, to the ends of the connecting rods concerned remote from the crank shafts.

If the dimensions of the machine fulfill said equations, the machine can be completely balanced, which will be explained more fully with reference to the drawing. It will be obvious that, if the dimensions of the machine do not accurately fulfill the said equations, balancing need not be completely disturbed.

The thermodynamic reciprocating machine according to the invention may be employed with particular success as a cold-gas refrigerator. In this case it is particularly desirable for the stroke volume of the piston to exceed the stroke volume of the displacer piston with a view to the high temperature differences between the space between the piston and the displacer and the space above the displacer.

The thermodynamic reciprocating machine according to the invention, intended for use as a cold-gas refrigerator and comprising one or more cylinders in which a piston and a displacer are adapted to reciprocate with a relative phase difference, is characterized in that each of the pistons is connected with that connecting rod mechanism which has its connecting rods connected with the crank shafts by the crank journals farthest remote from the centre line of the crankshaft concerned, whereas each of the displacers is connected with the connecting rods of the other mechanism and in that the connecting rods have a length such that each of the pistons performs a larger stroke than the co-operating displacer.

In an advantageous embodiment the thermodynamic reciprocating machine according to the invention intended for use as a cold-gas refrigerator is characterized in that, in operation, the absolute temperature in the space of each cycle of the higher temperature is at least 3 six times higher than absolute temperature in the space of the same cycle having the lower temperature.

A further advantageous embodiment of the thermodynamic reciprocating machine according to the invention is characterized in that, in operation, the absolute temperature of the space of each cycle having the lower temperature is at the most 40 Kelvin.

Particularly in obtaining said low temperatures and with a view to the required high temperature difference between the said space and the hotter space of each cycle it is important that the stroke volume of the piston should exceed that of the displacer.

The invention will he described more fully with reference to the drawing, which is not given to scale and has to be regarded by way of example.

FIG. 1 shows a thermodynamic reciprocating machine of the displacer-piston type in a sectional view.

FIGS. 2 and 2a illustrate a few embodiments of crank shafts suitable for use in the thermodynamic reciprocating machine of FIG. 1.

FIGS. 3 and 4 show a few further embodiments of the driving gear used in the thermodynamic reciprocating machine of FIG. 1 in a diagrammatic view.

FIG. 5 is a sectional view of a thermodynamic reciprocating machine, in which a plurality of relatively co-opcrating pistons and displacers arranged on yokes and performing unequal strokes.

In the drawing reference numeral 1 designates a cylintier of a thermodynamic reciprocating machine, in which a displacer 2 and a piston 3 are adapted to reciprocate with a phase difference. The upper end of the cylinder is formed by a cylinder head 4, provided on its inner side with vanes 5, and on the outer side with vanes 6. A lining 7 constitutes the partition between the vanes 5 and a regenerator 8 and the interior of the cylinder. The cylinder is furthermore provided with holes 9 communicating with a space comprising vanes 10, secured to a body 11, which is provided on its outer sides with ribs 12, said vanes and ribs forming a cooling system. Instead of the vanes 12 the body 11 may be provided with cooling-water ducts. The cylinder head 4 is surrounded by a body 13 comprising a burner 14 (shown diagrammatically). The combustion bases brush along the vanes 6 and leave the body 13, after having given off their heat, through an outlet duct 15. The cylinder head 4 is secured by bolts 16 to the body 11, which is connected by bolts 17 with a crankcase 18. These bolts 17 furthermore secure. the cylinder 1 rigidly to the crankcase 18. The piston 3 is provided with a hollow piston rod 19. The heads 21 of two connecting rods 22 are adapted to rotate about a shaft 20, which is rigidly secured to the piston rod 19 and a displacer rod 23, secured to the displacer 2, is taken through the piston rod 19 and the shaft 20. The connecting rods 22 have furthermore heads 24, whichare adapted to rotate about crank journals 25. The crank journals 25 are secured to cranks 26, which are connected with crank shafts 27. The cranks 26 are furthermore provided with crank journals 28, about which the. heads 29 of the connecting rods 30 are arranged. The connecting rods 30 are provided at the other end with heads 31, which are rotatably fastened to shafts 32, journalled in a yoke 33, to which the displacer rod 23 is secured. The crank shafts 27 are intercoupled by. interengaging gear wheels 34, fastened rigidly to said shafts. The crank shafts 27 may have the constructions shown in FIGS. 2 and 2a. To" the crank shafts 27 isv furthermore secured a counterweight 35.

The crank: casev 18 of this embodiment of the thermodynamic reciprocating machine is provided with a partition. 37 separating a space 38 from the space accommodating the driving gear. The space 38 communicates through openingsv 39 freely with the space below the piston and is filled with the working medium. The piston rod 19 and the displacer rod 23 are connected through an opening 40 in the partition with the driving gear. In

the opening 40 the piston rod 19 is surrounded by a gas-tight seal 41 and between the piston rod 19 and the displacer rod 23 there is also provided a gas-tight seal. It will be obvious that the space accommodating the driving gear need not be gas-tight, so that a pressure corresponding with the atmospheric pressure may prevail therein.

The crank journals 25 and 28 are located at distances r and r respectively from the centre lines of the crank shafts concerned. The connecting rods 22 and 30 have lengths l and 1 respectively. The eccent-ricities of the heads of the connecting rods 21 and 31 are designated in the figure by 2 and e respectively. The dimensions of the driving gear are chosen so that they fulfill the fol lowing equation:

The masses of the parts, for example the piston and the displacer, the piston rod and the displacer rod and the yoke, moving in the direction of the centre line of the machine, are chosen so that the masses to be supposed concentrated at the ends 21 and 31 of the connecting rods 22 and 30 respectively for balancing purposes are inversely proportional to the equation referred to above which means that, for example, r :r =m :m

The possibility of a complete balancing of the structure described above will appear from the following.

The driving gear is completely symmetrical to the centre line of the machine, so that in a direction at right angles to the centre line of the machine the forces occurring in the two halves of the driving gear compensate each other completely. In balancing only the forces occurring in the direction of the centre line of the machine need be considered. Since, as stated above, the two machine halves are identical, it will suflioe to consider one of them. The masses of the moving parts are considered concentrated at the following points.

The mass m at point 20, which mass corresponds with half of the mass of the piston and the piston rod plus that part of the mass of the connecting rod which may be considered concentrated at the end 21 of the connecting rod 22 in accordance with the lever principle.

The mass m at crank journals 25, which mass corresponds with the other part of the mass of the connecting rods 22, which may be considered concentrated at said point in accordance with the lever principle.

The mass m at point 36, at a distance r, from the centre line of the crank shaft, which mass corresponds with the rotating mass of the crank.

The mass m at point 32, which mass corresponds With half the mass of the displacer 2, the displacer rod 23 and the yoke 33, plus that part of the mass of the connecting rod 30 which may be considered concentrated at point 32 in accordance with the lever principle.

The mass m at the crank journal 28, which mass is equal to that part of the mass of the connecting rod 30 which may be considered concentrated at point 28, in accordance with the lever principle.

The mass m is the mass of the counterweight arranged at a point at a distance r from the centre line of the crank shaft.

From FIG. 1 it follows that thedistancesof the various masses from the plane going through the centre lines of the crank shafts may be defined as follows:

It follows therefrom that:

Since the dimensions of the driving gear fulfill the equation:

and

from which it follows that the angles 6 and are equal to each other and depend in the same manner upon the angle I Cos 0 and cos 6 may therefore be written as a progression development of the angle I', i.e.:

After substitution of this value for cos 0 the equations for the distances of the various masses from the plane going through the centre lines of the crank shafts are as follows:

operative in the direction of the centre line of the machine are obtained:

+500 cos I -H 211 sin m m :i =m 7 (w sin I -l-d; cos I 4 4= 4 (w sin I -Hi: cos \I/) m :ii =m 7 (w sin I+(;J cos I ms e= e ol w2 sin 'd-70) 005 +Y0)l For a complete balancing of the driving gear the sum of the forces resulting from the higher harmonics must be zero. The sum of the higher harmonic forces appears, in this case, to be equal to:

Since the driving gear is dimensioned so that,

l /l =m /m is fulfilled and hence also: m l ==m l it is found that the sum of the higher harmonic forces is zero, so that the condition of a comlete balancing of the driving is fulfilled.

In a generally known manner the value of the mass m and the angle 'y of the counterweight can be determined.

If the dimensioning of the driving gear does not completely correspond to the above values of the connecting rods, the masses or the radii of the cranks, small forces may result therefrom. These small forces are in many cases still admissible. Even a deviation of about 10% from the dimension ratios given above may in many cases be acceptable for a machine.

FIG. 3 shows diagrammatically a slightly modified form of a driving gear suitable for use in a thermodynamic reciprocating machine according to the invention. To the dimensions of the connecting rods l and 1 the radii of the cranks r and r and the eccentricities e and e applies the same law of proportion as in the structure shown in FIG. 1. The connecting rods 122 are, however, also connected with a yoke, to which the connecting rod 119 of the piston 103 is secured.

To the other yoke 133 is secured the displacer rod 123. The displacer 102, coupled with said displacer rod 123, is constructed as a so-called step displacer. Such a displacer is particularly suitable with the production of low temperatures. In the construction of the displacer shown in FIG. 3 the volume variation of the space is substantially in equal phase with that of the space 151, so that in the space 150 mainly expansion will occur, whilst cold is supplied at a higher temperature level than with the expansion in the space 151.

The displacer may, however, also be constructed so that the volume variations of said spaces are in opposite phase, so that in the intermediate space 150 mainly compression occurs.

It will be obvious that although, as shown in the drawing, the yokes are provided with only one set of cooperating pistons and displacers, one yoke may, if desired, cooperate with a plurality of pistons and the other yoke with a corresponding number of displacers. It is even possible, to connect, apart from the piston rod or the displacer rod, one or both yokes with the connecting rod of a further piston-like body, for example the piston of the compressor.

FIG. 4 shows diagrammatically a driving gear which may also be employed in a thermodynamic reciprocating machine in which the piston and the displacer perform unequal strokes. With this embodiment the connecting rods 222 and 230 are coupled with crank journals, which are connected with cranks which are at an angle go to each other. The driving gear shown in this figure does no longer fulfil the conditions for a complete balancing. With this driving gear, however, the piston and the displacer can perform unequal strokes.

FIG. 5 shows a further embodiment of a driving gear which can be completely balanced. The ends of the connecting rods 322 are interconnected by a yoke 321 and the ends of the connecting rods 330 are interconnected by a yoke 333. The directions of the connecting rods 322 and 330 differ from those of the embodiments in FIGS. 1, 3 and 4, since the ends of said connecting rods are remote from the centre line of the machine. This driving gear can be completely balanced, since the dimensions again fulfil the equation: r :r =l :l =e :e =m :m From this example it appears furthermore that without 7 any objection a plurality of co-operating pistons and displacers may be provided on the yokes 321 and 333; in this case the yoke 333 has the displacers 302 with the displacer rods 323 and the yoke 321 has the pistons 303 with the piston rods 319.

What is claimed is:

1. A thermodynamic reciprocating machine comprising a cylinder, a piston and a displacer constituting pistonlike elements, two crankshafts arranged in a substantially parallel relationship, means intercoupling said crankshafts to rotate the same in synchronism in opposite directions with equal angular velocities, said crankshafts being located symmetrically to a plane parallel to the center lines of the crankshafts and going through the longitudinal axis of the machine, a piston rod for each piston-like element, a multiplicity of connecting rod mechanisms, a plurality of cranks and crank journals for operatively connecting to at least a pair of said connecting rods, the ends of the connecting rods of one of the connecting rod mechanisms remote from said crankshafts being intercoupled and located on one side of theplane going through the center lines of said crankshafts, and the corresponding ends of other connecting rods of another of the connecting rod mechanisms being intercoupled and located on the other side of said plane going through the center lines of said crankshafts, said crank journals of each of the crankshafts connecting the crankshafts and the corresponding connecting rods of said one and said other connecting rod mechanisms and being spaced apart from said center lines, said connecting rods having such lengths that the piston-like elements connected with one connecting rod mechanism and the pistonlike elements connected with the other connecting rod mechanism perform unequal strokes, the dimensions of the operative parts of said machine fulfilling the following equation:

wherein 1' and r are the distances of the crank journals from the center lines of the crankshafts, which crank journals connect the connecting rods of the first and second mechanism with the crankshafts respectively,

1 and 1 are the lengths of theconnecting rods of the first and second mechanism respectively,

e and e are the distances of the projections of the ends of the connectingrodstof the first and second mechanism respectively into the plane going through the center lines of said crankshafts from the center line of said shaft, concerned and m andm are the masses of theparts reciprocating in the direction of the center lineof saidmachine, which. parts are connected with the connecting rods of the.

first and second mechanism respectively. plus that part of the mass of the connecting rod to be added to the ends of the connecting rods remotes-from the crankshaft.

2. A. thermodynamic reciprocating machine comprising a cylinder, a piston and adisplacer. constitutingpistom like elements, two crankshafts arranged in a substantially parallel relationship, means, intercoupling said crank,-

shafts to rotate the same in synchronism in opposite directions with equal angular velocities, said crankshafts being located symmetrically to a plane parallel to the center lines of the crankshafts and going through the longitudinal axis of the machine, a piston rod for each piston- 1ike element, a multiplicity of connecting rod mechanisms, a plurality of cranks and crank journals for operatively connecting to at least a pair of said connecting rods, the ends of the connecting rods of one of the con- :necting rod mechanisms remote from said crankshafts Tbeing intercoupled and located on one side of the plane going through the center lines of said crankshafts and the corresponding ends of other connecting rods of another of the connecting rod mechanisms being intercoupled and located on the other side of said plane going through the center lines of said crankshafts, said crank journals of each of the crankshafts connecting the crankshafts and the corresponding connecting Tods of said one and said other connecting rod mechanisms and being spaced apart from said center lines, said connecting rods having such lengths that the piston-like elements connected with one 7 connecting rod mechanism and the piston-like elements connected with the other connecting rod mechanism perform unequal strokes, the radial distance between the point at which said connecting rod is connected to said crankshaft and the rotative center of said crankshaft, and the angle between said connecting rod and piston rod is such that the piston performs a greater stroke than the displacer, the dimensions of the operative parts of said machine fulfilling the following equation: r :r =l :l =e :e =m 2m wherein r and r are the distances of the crank journals from the center lines of the crankshafts, which crank journals connect the connecting rods of the first and second mechanism with the crankshafts respectively, 1 and I are the lengths of the connecting rods of the first and second mechanism respectively, e and a are the distances of the projections of the ends of the connecting rods of the first and second mechanism respectively into the plane going through the center lines of said crankshafts from the center line of said shaft concerned and m and m are the masses of the parts reciprocating in the direction of the center line of said machine, which parts are connected with the connecting rods of the first and second mechanism respectively plus that part of the mass of the connecting rod to be added to the ends of the connecting rods remote from the crankshaft.

References Cited by the Examiner UNITED STATES PATENTS 2,616,248 11/1952 DeBrey et a1. 6024 2,963,854 12/1960 Meijer 60-24 3,074,229 l/1963 Baas et al 60-24 SAMUEL LEVINE, Primary Examiner.

JULIUS E. WEST, Examiner. 

1. A THERMODYNAMIC RECIPROCATING MACHINE COMPRISING A CYLINDER, A PISTON AND A DISPLACER CONSITUTING PISTONLIKE ELEMENTS, TWO CRANKSHAFTS ARRANGED IN A SUBSTANTIALLY PARALLEL RELATIONSHIP, MEANS INTERCOUPLING SAID CRANKSHAFTS TO ROTATE THE SAME IN SYNCHRONISM IN OPPOSITE DIRECTIONS WITH EQUAL ANGULAR VELOCITIES, SAID CRANKSHAFTS BEING LOCATED SYMMETRICALLY TO A PLANE PARALLEL TO THE CENTER LINES OF THE CRANKSHAFTS AND GOING THROUGH THE LONGITUDINAL AXIS OF THE MACHINE, A PISTON ROD FOR EACH PISTON-LIKE ELEMENT, A MULTIPLICITY OF CONNECTING ROD MECHANISMS, A PLURALITY OF CRANKS AND CRANK JOURNALS FOR OPERATIVELY CONNECTING TO AT LEAST A PAIR OF SAID CONNECTING RODS, THE ENDS OF THE CONNECTING RODS OF ONE OF THE CONNECTING ROD MECHANISMS REMOTE FROM SAID CRANKSHAFTS BEING INTERCOUPLES AND LOCATED ON ONE SIDE OF THE PLANE GOING THROUGH THE CENTER LINES OF SAID CRANKSHAFTS, AND THE CORRESPONDING ENDS OF OTHER CONNECTING RODS OF ANOTHER OF THE CONNECTING ROD MECHANISMS BEING INTERCOUPLED AND LOCATED ON THE OTHER SIDE OF SAID PLANE GOING THROUGH OF EACH OF THE CRANKSHAFTS CONNECTING THE CRANKJOURNALS OF EACH OF THE CRANKSHAFTS CONNECTING THE CRANK- 